Sputtering apparatus have been extensively used in the production of thin films of magnetic material. In depositing these films, a variety of properties are of concern, and to achieve these properties, the films are frequently deposited in the presence of an external magnetic field. In the past, permanent magnets have been used to establish the needed magnetic field. In order to increase the processing rate in manufacturing, the substrates, upon which the thin films of magnetic material are deposited, are rotated. This causes substantial fluctuations in the plasma density due to the interaction between the magnetic field and the free electrons of the plasma. Consequently, uniformity of the film properties is poor and difficult to control.
An attempt has been made to introduce electromagnets to sputtering systems. For example, Boucher et al., U.S. Pat. No. 4,094,764, "Device for Cathodic Sputtering at a High Deposition Rate", issued June 13, 1978, disclose a permanent magnet in the vicinity of the target electrode in order to increase the sputtering rate, and it is disclosed that the magnetic field could as well be produced by a solenoid coil. Greve et al., U.S. Pat. No. 4,247,383, "Cathodic System with Target, for Vacuum Sputtering Apparatus for the Application of Dielectric or Nonmagnetic Coatings to Substrates", issued Jan. 27, 1981, show a sputtering apparatus in which a planar coil is used in conjunction with the target electrode to produce increased atomization and therefore a greater sputtering rate for sputtering a dielectric or nonmagnetic coating.
Setoyama et al., U.S. Pat. No. 4,673,482, "Sputtering Apparatus", issued June 16, 1987, disclose a sputtering apparatus for sputtering magnetic thin films in which a pair of coils outside the vacuum chamber produces a magnetic field which extends into the vacuum chamber. The substrate upon which the magnetic thin film is to be deposited is mounted within the vacuum chamber, and a permanent magnet plate is mounted parallel to the substrate surface to improve the uniformity of the magnetic field at the substrate surface.
None of the references discloses or suggests a polygon-shaped planar electromagnetic coil adjacent to a surface of the substrate for maintaining the orientation of deposited films during relative motion between the target and the substrate upon which the magnetic film is deposited.